Most supermarket chicken is still contaminated with the food poisoning bug campylobacter, according to the results of a controversial new retail survey published on Tuesday by the Food Standards Agency.

The survey tested samples of raw chicken bought at all the leading UK supermarkets and at butchers in spring of this year. It found that 59% of birds carried the potentially deadly bacteria, and 16% were heavily contaminated. More than two-fifths of retail chickens fell into the medium or heavily contaminated categories.

The food watchdog had promised to name and shame individual retailers and processors for their contamination counts when it published its results – they are first-quarter figures from a survey that will continue through the year – but it backed down from after intense pressure from the food industry and other government departments last month.

The agency decided that it needed to wait for a larger number of results before going ahead, but consumer groups and leading food policy experts condemned the climbdown as putting industry interests ahead of those of the public.

Campylobacter is the most common form of food poisoning in the UK . An estimated 280,000 people a year are made ill by it, and the majority of infections are attributable to contaminated chicken. The FSA has said the illness is its top priority, and the naming and shaming was part of its campaign to force the industry to act after a decade of little progress. The last FSA survey in 2008 found that 65% of birds were contaminated.

The bug, which is carried in the guts and faeces of poultry, is killed by cooking but can be spread from raw meat in the kitchen. Current advice is that chicken should not be washed before cooking as this can spread contamination to other surfaces.

A Guardian investigation last month revealed a number of points in the chicken production chain at which strict hygiene rules to limit the spread of the bug can break down. It led to the health secretary, Jeremy Hunt, demanding FSA audits of two leading poultry factories and emergency inspections by leading supermarkets. The FSA audits found the factories good and generally satisfactory.

The agency's chief executive, Catherine Brown, said: "This survey is an important part of the work we are doing to tackle campylobacter. It will help us measure the impact of interventions introduced by producers, processors, and retailers to reduce contamination." The FSA would release information on the retailers with the worst rates of contamination "as soon as we have enough date to robustly compare levels", she said.

The consumer watchdog Which? said the levels of campylobacter revealed by the new survey were unacceptably high.

​"The FSA must now publish the names of the retailers so consumers are aware of the best and worst-performing shops.

"Campylobacter is responsible for the deaths of 100 people every year, so much more must be done to minimise the risk of contamination at every stage of production,"​ said Richard Lloyd, the executive director of Which?.